The invention relates to a display device comprising at least one line modulation panel and at least two projection elements, in which, in operation, an image having a relatively high resolution in a relatively small field of view is presented to a first eye by means of the first projection element, while an image having a relatively low resolution in a relatively large field of view is presented to a second eye by means of the second projection element.
In such a display device, which is known from U.S. Pat. No. 5,912,650, an image having a relatively high resolution for a relatively small field of view or an image having a relatively low resolution for a relatively large field of view is alternately generated by means of the light modulation panel. The display device is provided with means for alternately presenting the first or the second image to the first or the second eye. Thus, images having a relatively high resolution in a relatively small field of view are observed by one eye, while images having a relatively low resolution in a relatively large field of view are observed by the other eye.
The images presented to both eyes are combined in the human brain to an image having a relatively large field of view with a relatively low resolution in which a relatively small field of view with a relatively high resolution is located.
The display device described in U.S. Pat. No. 5,912,650 has, however, a plurality of drawbacks. The light modulation panel is to be controlled alternately for generating an image with a relatively high resolution in a relatively small field of view and for generating an image with a relatively low resolution in a relatively large field of view. Consequently, the control of the light modulation panel is relatively complicated. Moreover, also the part corresponding to the small field of view is illuminated by the second projection element, which part is replaced in the human brain by the image having a relatively high resolution and formed by means of the first projection element.
Consequently, an optimal illumination is not obtained.
It is an object of the invention to provide a display device in which images having a relatively low resolution in a relatively large field of view are generated in a simple manner, while a relatively small field of view having a relatively high resolution is located in the large field of view.
In the display device according to the invention, this object is achieved in that the second projection element with the large field of view is provided with means for masking a part of the large field of view, which part substantially corresponds to the small field of view.
Since the part of the large field of view corresponding to the small field of view is masked by means of the second projection element, both projection elements can be optimized for the function to be performed by the relevant projection elements, namely for generating an image with a relatively high resolution in a relatively small field of view, or for generating an image with a relatively low resolution in a relatively large field of view, with one image being presented to one eye and the other image being presented to the other eye.
An embodiment of the display device according to the invention is characterized in that each projection element is provided with a separate light modulation panel in which the image for a relatively small field of view can be generated by means of the first light modulation panel, while the image for the relatively large field of view can be generated by means of the second light modulation panel.
In this way, images can be continuously presented to both eyes.
A further embodiment of a display device according to the invention is characterized in that the second projection element is provided with the light modulation panel, a lens preceding the light modulation panel, a concave mirror surrounding the light modulation panel and a layer preceding the lens, which layer is reflective to light beams from the lens towards the concave mirror, said layer being provided with a masked part for masking the desired part of the large field of view.
A relatively large field of view can be generated in a simple manner by means of such a projection element which is provided with a concave mirror. The part to be withdrawn from the large field of view is effectively masked by the masked part provided on the layer.
Moreover, the masking prevents light rays from the light modulation panel from directly reaching the eye. These light rays do not contribute to the formation of the image on the retina of the eye. They disturb the image. This is also referred to as stray light.
In principle, a 100% transmission for the light rays from the light modulation panel to the pupil of the eye can be obtained by the masking effect.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.